Testing circuits on substrate

ABSTRACT

The invention provides a method of testing a circuit on a substrate. Generally speaking, a substrate is located in a transfer chuck, a surface of a test chuck is moved into contact with a substrate, the substrate is secured to the test chuck, the test chuck is moved relative to the transfer chuck so that the substrate moves off the transfer chuck, terminals on the substrate are moved into contact with contacts to electrically connect the circuit through the terminals and the contacts to an electric tester, signals are relayed through the terminal and the contacts between the electric tester and the circuit, the terminals are disengaged from the contacts, and the substrate is removed from the test chuck.

This application is a divisional application of U.S. patent applicationSer. No. 10/035,508, filed Oct. 22, 2001, now U.S. Pat. No. 6,861,859.

BACKGROUND OF THE INVENTION

1). Field of the Invention

This invention relates to a method and apparatus for testing circuits onsubstrates.

2). Discussion of Related Art

Electronic circuits are often manufactured on semiconductor wafers. Asaw is then used to cut the wafer into individual dies, each carrying arespective circuit. The dies are then mounted to other substrates whichprovide both structural support and electric communication to otherdevices.

It is often required to test such circuits at various stages duringmanufacture and before they are sold. An apparatus used for testing sucha circuit usually includes a plurality of spring contacts which arebrought into contact with terminals connected to the circuit. Electronicsignals are then relayed through the contacts and terminals between anelectric tester and the circuit so as to test functional integrity ofthe circuit.

SUMMARY OF THE INVENTION

The invention provides a method of testing a circuit on a substrate. Forexample, a substrate is located in a transfer chuck, a surface of a testchuck is moved into contact with a substrate, the substrate is securedto the test chuck, the test chuck is moved relative to the transferchuck so that the substrate moves off the transfer chuck, terminals onthe substrate are moved into contact with contacts to electricallyconnect the circuit through the terminals and the contacts to anelectric tester, signals are relayed through the terminals and thecontacts between the electric tester and the circuit, the terminals aredisengaged from the contacts, and the substrate is removed from the testchuck.

According to one aspect of the invention an image is recorded of asurface of the substrate while still on the transfer chuck, for examplewhile moving off the transfer chuck.

According to another aspect of the invention, an image is recorded of asurface of the substrate in a single pass.

According to a further aspect of the invention, a plurality ofsubstrates are simultaneously held by the test chuck and may besimultaneously scanned and may be simultaneously heated or cooled.

The invention also provides a corresponding apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of example with reference tothe accompanying drawings wherein:

FIG. 1 is a perspective view of an apparatus used for testing circuitson substrates according to an embodiment of the invention;

FIG. 2 is a view similar to FIG. 1 where a top plate is removed;

FIG. 3 is an end view of a portion of a transfer chuck of the apparatus;

FIG. 4 is a plan view of the transfer chuck illustrating loading of afirst substrate;

FIG. 5 is a view similar to FIG. 4 after the transfer chuck is moved andmore substrates are loaded in the transfer chuck;

FIG. 6 is an end view of the transfer chuck with the substrates thereon,further illustrating an thermal conditioning chuck;

FIG. 7 is a view similar to FIG. 6 after the thermal conditioning chuckis moved so as to elevate the substrates, and air is provided throughthe thermal conditioning chuck to heat the substrates;

FIG. 7A is an enlarged view of a portion of FIG. 7;

FIG. 8 is a perspective view similar to the perspective view of FIG. 2after the transfer chuck is moved off the thermal conditioning chuck andthe substrates are aligned with a test chuck;

FIG. 9 is an end view illustrating the transfer chuck and the testchuck;

FIG. 10 is a view similar to FIG. 9 after the test chuck is elevated soas to elevate the substrates, and a vacuum is applied to secure thesubstrates to the test chuck;

FIG. 11 is a perspective view illustrating how the test chuck removesthe substrates from the transfer chuck;

FIG. 12 is a side view illustrating components of the apparatus used tocapture a two-dimensional image of an upper surface of each substrate;

FIG. 13 is a view similar to FIG. 12 illustrating the location of thetest chuck after the images are captured and the substrates are alignedwith contacts;

FIG. 14 is a plan view illustrating an example of a substrate which istested utilizing the apparatus;

FIG. 15 is an enlarged view of a die and terminals on the substrate;

FIG. 16 is a perspective view illustrating movement of the test chuck toagain insert the substrates into the transfer chuck;

FIG. 17 is a perspective view illustrating the substrates after they arelocated in the transfer chuck but before they are removed therefromutilizing substrate removal apparatus; and

FIG. 18 is a view similar to FIG. 17 after one of the substrates isremoved from the transfer chuck and a further substrate is located onthe transfer chuck.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 illustrate apparatus 20 used for testing circuits onsubstrates, according an embodiment of the invention. The apparatus 20includes a support frame 22, and, either directly or indirectly mountedto the support frame 22, substrate feeding apparatus 24, a transferchuck 26, thermal conditioning apparatus 28, a platen 30, a test chuck32, a top plate 34, a probe substrate 36, contacts 38 (shown inexaggerated detail), an electric tester 40, and substrate removalapparatus 42.

The substrate feeding apparatus 24 includes a feed cartridge 46 and aconveyor system 48 located next to the feed cartridge 46. A plurality ofsubstrates are located in the feed cartridge 46. The substrates are thenfed one after another onto the conveyor system 48. The conveyor system48 transfers the substrates from the feed cartridge 46 to the transferchuck 26.

FIGS. 3 and 4 illustrate the transfer chuck 26 in more detail. Thetransfer chuck 26 has six slots 50A-F formed therein. Each slot, forexample, the slot 50B, has two opposing supports 52A and 52B with arespective gap 54 between the supports 52A and 52B.

A substrate 56A is fed from the conveyor system 48 into the slot 50A.The substrate 56A is dropped onto the supports 52A and 52B of the slot50A. A lower surface of the substrate 56A is then exposed to the gap 54.

As shown on FIG. 5, the transfer chuck 26 is movable in a direction 58relative to the support frame. The transfer chuck 26 is first moved sothat the conveyor system 48 is aligned with the slot 50B. Anothersubstrate 56B is then loaded into the slot 50B. The transfer chuck 26 isthen moved so that the slot 50C is aligned with the conveyor system 48.Another substrate 56C is then located in the slot 50C. The conveyor 48does not fill the slots 50D-F with substrates.

The transfer chuck 26 is then moved back into its position as shown inFIG. 4. As shown in FIG. 6, the substrates 56A-C are thereby locatedover an thermal conditioning chuck 60 of the thermal conditioningapparatus 28. The thermal conditioning chuck 60 has an upper side havingthree high surfaces 62 alternated by two low surfaces 64. Each highsurface 62 is located below a respective one of the substrates 56A-C. Anair outlet opening 66 is formed into a lower surface of the thermalconditioning chuck 60. Air suction openings 68 lead off the air outletopening 66 and have air entry points in the surfaces 62. Although notshown in FIG. 6, it should be understood that each surface 62 has aplurality of air suction openings 68 spaced from one another into thepaper.

The thermal conditioning apparatus also includes resistive elements 69Aand cooling passages 69B, which are located within the thermalconditioning chuck 60.

Air is then pumped in a direction 74 out of the air suction opening 66so that vacuums are created in the air suction openings 68 and on thelower surfaces of the substrates 56A-C. The vacuums secure thesubstrates 56A-C to the surfaces 62.

The thermal conditioning chuck 60 is movable relative to the supportframe 22 in a vertical direction 70. As shown in FIG. 7, such movementof the thermal conditioning chuck 60 moves the surfaces 62 in betweenthe gaps 54 so that each surface 62 contacts a respective lower surfaceof a respective one of the substrates 56A-C. Further movement of thethermal conditioning chuck 60 in the direction 70 elevates thesubstrates 56A-C from the supports 52A and 52B. The substrates 56A-C arestill laterally supported by sidewalls 72 extending upwardly from thesupports 52A and 52B.

As shown in FIG. 7A, each substrate 56 has one or more dies 108 on itslower surface. The surface 62 has a recess 78 between two ledges 80. Thedies 108 fit into the recess 78 when the surface 62 moves up. The ledges80 make contact with the substrate 56 next to the dies 108 and betweenthe supports 52A and B.

The substrates 56A-C are then either heated or cooled. The substratesmay be heated by applying a voltage so that current conducts through theresistive elements 69A. The resistive elements heat the thermalconditioning chuck 60, which in turn heats the substrates 56A-C.Alternatively, a cold fluid flowing through the passages 69B may coolthe thermal conditioning chuck 60 and the substrates 56A-C. As such, thesubstrates 56A-C can be heated or cooled to any selected temperaturebetween −55° and 150° C. Because the dies 108 (FIG. 7A) are in therecess 78, the material around the recess 78 assists in maintaining thetemperature of the dies 108 at a desired level, especially near edges ofthe substrate 56.

It takes approximately one minute to heat or cool the substrates 56A-C,whereafter the air flow is turned off. The thermal conditioning chuck 60is then moved in a direction opposite to the direction 70 so that thesubstrates 56A-C drop onto the supports 52A and 52B. The thermalconditioning chuck 60 is moved further down so that the surfaces 62 arelocated below the gaps 54.

As shown in FIG. 8, the transfer chuck 56 is moved in a direction 78 sothat the substrates 56A-C are moved off the thermal conditioning chuck60. The test chuck is movable on the platen 30 in horizontal x andy-directions and in a vertical z-direction. The test chuck 32 is firstaligned with the substrates 56A-C and then moved in a direction 30 andunderneath the transfer chuck 26. The test chuck 32 typically includes aforcer which rides on the platen 30, and is known in the art.

FIG. 9 illustrates the test chuck 32 located below the transfer chuck26. The test chuck 32 has an upper side having three higher surfaces 84with two lower surfaces 86 between them. Each higher surface 84 islocated directly below a respective one of the gaps 54. An air outletopening 88 is formed out of the test chuck 32. Air outlet passages 90are formed into the surfaces 84 and are connected to the air outletopening 88.

The test chuck 32 is movable in a vertically upward z-direction 92. Asshown in FIG. 10, such movement of the test chuck 32 moves the surfaces84 through the gaps 54 so that the surfaces 84 contact the lowersurfaces of the substrates 56A-C. Further movement of the test chuck 32in the z-direction 92 elevates the substrates 56A-C off the supports 52Aand 52B.

A vacuum is then created within the air outlet opening 88 which createsa vacuum in each one of the air outlet openings 90. The vacuums createdin the air outlet openings 90 suck the substrates 56A-C down onto thesurfaces 84. The substrates 56A-C are so secured to the test chuck 32.

The test chuck 32 includes a lower portion 32A and an upper portion 32B.The lower portion 32A is movable relative to the support frame. Theupper portion 32B is disengageably secured to the lower portion 32A, andis thus “carried” by the lower portion. The upper portion 32B has theraised and recessed formations 84 and 86. The upper portion 32B isdisengageable from the lower portion 32A to allow for interchangeabilitywith another upper portion 32B with raised and recess formations sizedfor accommodating other substrates having larger or smaller widths thanthe substrates 56A-C. The gaps 54 are also adjustable to match widths onraised formations on a selected upper portion 32B.

As shown in FIG. 11, the test chuck 32 is then moved in a horizontaly-direction 96. Such movement moves the substrates 56A-C out of theslots 50A-C.

As shown in FIG. 12, the apparatus also includes an image recordationdevice in the form of a line scanner 98 which is mounted in a stationaryposition to the support frame 22. The line scanner 98 has a lens 100.The lens 100 focuses on a line represented by a point 102 in FIG. 12 andextending into the paper. The line represented by the point 102 islocated approximately 2 cm to the left of a location 104 where thesubstrates 56 leave the transfer chuck 26, as measured in the direction96. One of the substrates 56 is approximately 20 cm long as measured inthe direction 96. An entire lower surface of the substrates 56 islocated on a respective upper surface of the test chuck 32.

Because of the relative lengths and distances, and in particular becausethe substrate 56 is longer than the distance between the locations 102and 104, the lens 100 begins to focus on an upper surface of thesubstrates 56 while it is still located over the transfer chuck 26 andas it moves off the transfer chuck 26. The lens 100 simultaneouslyfocuses on a line across upper surfaces of the substrates 56A-C in asimilar manner. A one-dimensional image of the upper surface of eachsubstrate 100 is taken along the line represented by the location 102,and provided by the line scanner 98 to an image capture device such asmemory of a digital camera. Movement of the substrates 56 in thedirection 96 moves the line represented by the location 102 across uppersurfaces of the substrates 56 so that two-dimensional areas of the uppersurfaces of the substrates 56 are scanned. A computer knows the speed atwhich the test chuck 32 moves in a direction 96 so that atwo-dimensional image of the upper surfaces of each of the substrates 56is rendered by logic of the computer.

The test chuck 32 is then further moved in the direction 96 until one ofthe substrates 56 is located below the contacts 38. It should be notedthat the substrates 56 are moved in unison and pass by lens 100 onlyonce. The test chuck 32 is thus not, for example, moved back and forthin the direction 96 and in a direction opposing the direction 96 pastthe lens 100. Because of a single pass past the lens 100, a very rough,although sufficient single image of upper surfaces of the substrates 56is created but no time is lost by again scanning upper surfaces of thesubstrates 56. The image is still accurate to approximately 12 microns,which is at least an order of magnitude more accurate than whatconventional handlers used for positioning of components or motherboardsand other purposes are designed to be capable of. (Multiple passes maybe required for other applications. For example, contacts on a wafer maybe too small to accurately scan in a single pass. Multiple scans may becarried out, with each subsequent scan being used to more accuratelylocate the contacts on the wafer.)

The test chuck 32 can then be moved in x-, y-, and z-directions so thateach one of the contacts 38 is brought into contact with a respectiveset of terminals on one of the substrates 56, followed by x-, y-, andz-movement of the test chuck 32 so that each one of the contacts 38contacts a respective terminal on the other substrate, followed then bythe third substrate. The contacts 38 are all electronically connected tothe tester 40 so that test signals can be provided between the tester 40and the terminals.

FIGS. 14 and 15 illustrate one of the substrates, for example thesubstrate 56A, in more detail. The substrate 56A includes a flexiblesheet 104, a plurality of rigid substrates 106, and a plurality ofelectronic dies 108. The rigid substrates 106 are mounted to theflexible sheet 104. A plurality of the dies 108 are mounted on andprotrude from a rear surface of a respective one of the rigid substrates106. An electronic circuit is formed on a frontal surface of each one ofthe dies 108. A plurality of terminals 110 are located on each die 108and are connected to the circuit formed in the respective die 108.

The contacts 38 shown in FIG. 13 make contact with the terminals 110.Electronic signals are transmitted between the electric tester 40 shownin FIG. 1 through the contacts 38 and the terminals 110 to and from thecircuit formed in the die 108. By relaying signals back and forth, thecircuit within the die 108 can be tested with the electric tester 40.Once the circuit is tested, the test chuck 32 is moved verticallydownward so as to disengage the terminal 110 from the contacts 36. Thetest chuck 2 is then moved in x- and y-directions to align terminals ofanother one of the dies 108 with the contacts 36, whereafter the testchuck 32 is moved vertically upward so as to engage the terminals of theother die 108 with the contacts 38. It may also be possible to test moreof the dies 108 at once.

Once the circuits in all the dies 108 are tested, the test chuck 32 ismoved in an x-direction so that each one of the substrates 56A-C isaligned with a respective one of the slots 50D-F. As shown in FIG. 16,the test chuck 32 is then moved in a direction 108 so that thesubstrates 56A-C are located in the slots 50D-F respectively. The vacuumon the test chuck is then released so that the substrates 56A-C arereleased from the test chuck 32. The test chuck 32 is then dropped sothat the substrates 56A-C drop into supports of the slots 50D-F.

As shown in FIGS. 17 and 18, the substrate removal apparatus 42 includesa retracting tool 110, a conveyor system 112, and a removal cassette114. The retracting tool 110 is first used to move the substrate 56Aonto the conveyor system 112. The conveyor system then moves thesubstrate 56A into the removal cassette 114. While the substrate 56A ismoved into the removal cassette 114, another substrate 56D is moved intothe slot 50A.

The transfer chuck 26 is then moved in a direction illustrated by thedirection 58 in FIG. 5 so that the substrates 56B and 56C are removedwhile additional substrates are located in the slots 50B and 50C.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative and not restrictive of the current invention, andthat this invention is not restricted to the specific constructions andarrangements shown and described since modifications may occur to thoseordinarily skilled in the art.

1. An apparatus for testing circuits on substrates comprising: a supportframe; a transfer apparatus capable of holding at least one of aplurality of separate substrates; a test chuck located on the frame,having a surface with a plurality of raised formations alternated by aplurality of recesses, and being movable relative to the transferapparatus so that surfaces of each raised formation move into contactwith a respective substrate, the substrates being simultaneouslysecurable to the test chuck, each substrate to a respective surface of arespective raised formation, the test chuck being movable relative tothe transfer chuck so that the substrates move off the transfer chuck; aplurality of contacts secured to the support frame, the test chuck andthe contacts being movable relative to one another so that the contactscontact terminals on the substrates; and an electric tester connected tothe contacts so that signals can be relayed through the terminals andthe contacts between the electric tester and the circuit.
 2. Theapparatus of claim 1 wherein the transfer apparatus is stationary. 3.The apparatus of claim 1 wherein the test chuck includes a first portionwhich is movable relative to the frame and a second portion which isdisengageably secured to the first portion, the second portion havingthe raised and recessed formations.
 4. The apparatus of claim 1 whereinat least one of the raised formations has a recess into which at leastone of the substrates is located.
 5. The apparatus of claim 4 whereinthe second portion is configured to allow for interchangeability with athird portion that is to be disengageably secured to the first portionand replacing the second portion.
 6. The apparatus of claim 5 whereinthe third portion further includes raised and recessed formations sizedto accommodate at least one substrate.
 7. The apparatus of claim 6wherein the third portion is configured to accommodate at leastsubstrate having a larger or smaller widths than the substrates securedto the second portion.
 8. The apparatus of claim 7 wherein the secondportion is configured to accommodate a first plurality of the substratesand the third portion is configured to accommodate a second plurality ofthe substrates having larger or smaller widths than the first pluralityof the substrates.